It is well known to those skilled in the art that gelled water soluble polymers are useful in enhanced oil recovery operations. They have been used to alter the permeability of underground formations in order to enhance the effectiveness of water flooding operations.
The polymers along with an appropriate crosslinking agent are injected in an aqueous solution into the formation. They percolate into and gel in the regions having the highest water permeability. Any fluids injected into the formation in subsequent flooding operations will then be diverted away from the gels into regions of the formation having a lower water permeability.
A water-dispersible phenolic compound and a water-dispersible aldehyde have been used together as crosslinking agents for the gelation of water soluble polymers in enhanced oil recovery operations. For example, U.S. Pat. No. 4,799,548 discloses using a phenolic compound and an aldehyde for the formation of gelled water soluble polymers. However, the water soluble polymers gel fairly quickly, together with these compounds, after being injected into the formation. Quite often only the regions near the well bore are treated because the polymers gel before they have an opportunity to permeate throughout the entire formation. Furthermore, the polymers form gels that do not withstand the reservoirs' high temperature and high salinity environment over a long period of time to effectively alter the permeability of the underground formations. These gelled polymers are exposed to numerous mechanical forces within the formation which tend to promote the breakdown of the gels. When the gels break down, oil production decreases and it is necessary to retreat the formation with more water soluble polymers.
It would therefore be a significant contribution to the art to have a composition that would delay the rate of gelation of the water soluble polymers and a process that would increase the gel strength of water soluble polymers.